Method and apparatus for deep gas well completions

ABSTRACT

A tubular assembly having spaced-apart receptacles with polished bores is disposable in a well bore cementing dementing in place with the receptacle bores disposed above and below a producing formation. Upper and lower seal assemblies which are slidably and sealingly receivable in the spaced-apart receptacle bores are carried by a &#39;&#39;&#39;&#39;long&#39;&#39;&#39;&#39; tubing string and close off the receptacle bores to form an enclosed volume and provide a fluid conduit for fluids below the lower seal assembly. The upper seal assembly has an opening therethrough to the enclosed volume and is connectable to a &#39;&#39;&#39;&#39;short&#39;&#39;&#39;&#39; string of tubing. The effective cross-sectional area across the lower seal assembly is made equal to the effective cross-sectional area across the upper seal assembly by adjustment of the area of the opening through the upper seal assembly. The balancing of the effective cross-sectional areas eliminates movement of the seal assemblies during treating operations and eliminates the need for equipment to anchor the seal assemblies during treating operations.

166307Q SR lO-'22-7 OR 39842-1912 METHOD AND APPARATUS FOR DEEP GAS WELL COMPLETIONS [76] Inventor: Hiram E. Lindsey, Jr., c/o MWL Tool & Supply Co., PO. Drawer 631, Midland, Tex.

22 F1166: Sept. 4, 1973 211 App]. No.2 394,148

52 us. 01 166/307, 166/305 R; 166/191,

Primary Examiner-Stephen J. Novosad [57] ABSTRACT A tubular assembly having spaced-apart receptacles with polished bores is disposable in a well bore cementing dementing in place with the receptacle bores disposed above and below a producing formation.

Upper and lower seal assemblies which are slidably and sealingly receivable in the spaced-apart receptacle 1 313 1 bores are carried by a long" tubing string and close [51] Int. E21 b 43/27, E21b 33/ 10, 1 off the receptacle bores to form an enclosed volume [58] Field of Search 166/305 R, 307, 308, 313, 166/191, 127, 189, 315,115

[56] References Cited and provide a fluid conduit for fluids below the lower seal assembly. The upper seal assembly has an opening therethrough to the enclosed volume and is connectable to a short string of tubing.- The effective crosssectionalarea across the lower seal assembly is made UNITED STATES PATENTS equal to tlhe effegfiv; crczlss-sectionalfagea acres; tllle 7 upper sea assem y y a justment o t e area 0 t e 72231133 311322 321211'1111::::::"""""":::::: 122/13 l evening through t upper sealassemblye e 219501761 8/l960 Brown at a. 166/313 mg of the effective cross-sectionalareas' eliminates. 3,115,185 12/1963 Brown 166/313 ux mvemem of the Seal assemblles durmg p 32, ,94 5 9 g er a1, 166/305 R x ations and eliminates the need for equipment to an- 3,170,518 2/1965 Brown 166/313 chor the seal assemblies during treating operations. 3,330,360 7/1967 Young L 166/3l3 X 3,797,573 3/1974 Crowe... 166/313 9 Clalms, 2 Drawing Flgures 3,799,268 3/1974 Cochran 166/313 -ME THOD AND This invention relates to methods and apparatus for use in oil and gas wells, andmore'particularly, for deep gas well Completions where long strings of tubing, high pressure and temperatures, huge stimulation treatments and high-production rates give rise to unusual problems. i

Multiple completions for deep gas well production have prompted the development of novel systems and apparatus for more efficient and economical operations. One such system is illustrated in U.S. Pat. No. 3,640,341 where a dual completion system employs a tubular receptacle below a liner hanger. A permanent production packer is anchored in the tubular receptacle and'a sealing assembly is slidingly and sealingly received in the upper packer bore. If it is desired to'stimulate this well by acidizing or work over the well using packers, plugs, bits, perforating tools or the like, it is necessary to'remove the sealing assembly. If the'assem- ,bly is not removed and hydraulic pressure is introduced between the upper sealing assembly and the production packer, the hydraulic forces generated will move the upper sealing assembly in an upward direction unless it is latched or anchoredin the production'packer. Alternatively, it has been proposedv to use hold-down means on the upper seal assembly which are hydraulically actuated to anchor a sealing assembly relative to the receptacleb-Both .of these systemsare subject to malfunctions because of mechanical complexity, the equipment cost is increased, and the operationis more complex to perform. v I T SUMMARY OF THE PRESENT INVENTION- The present invention involves the location in a borehole of upper and lowerpacker bore receptacles, each having packer bores so that such packer bores straddle an earth strata for the production of hydrocarbons- The receptacles are cemented. at their locations and the earth strata intermediate of the receptacles is-placed into fluid communication'with a bore of tubular pipe or casing connecting thereceptacles. Thepacker bores of the receptacles are closed off with packing means associated with a string of tubing to form an enclosed volume between the packer bores of the upper and lower receptacles and the bore of the connecting pipe or casing. The enclosed volume has its ends defined by the cross-sectional areas of the packer bores inthe upper and lower receptacles exclusive of the cross-sectional area of such string of tubing.

Well treating fluids under pressure are introduced through the upper packing means to said enclosed volume where the cross-sectional areas of the upper and lower receptacles are adjusted relative to one another to have substantially equal areas thereby balancing the upper and lower areas and equalizing the upward and downward forces on the string of tubing within the enclosed volume.

The apparatus includesa packer bore receptacle assembly which has upper and lower packer bore receptacles. Packer means including an upper packer sealing assembly and a lower packer sealing assembly are constructed and arranged for a sliding and sealing reception respectively in the packer bores of the upper-and lower receptacles. The sealing assemblies are coupled toone another and spaced-apart by a section of tubing so that when the upper packer sealing assembly and the lower packer sealing assembly are slidingly and sealingly received in the respective packer'bores that upper and lower cross-sectional areas are defined. The coupling of various parts herein describedcan be by any sectional area whereby the effective areas ofthe upper and lower cross-sectional areas are substantially equal.

For a better understanding of the present invention, together with other and further objects and features thereof, reference is had to the following description taken in connection with the accompanying drawing,

. pended claims." A

the scope of the invention being pointed out in the ap- BRIEF DESCRIPTION or THE. DRAWINGS I Referring to the drawings: FIG. 1 is aview in vertical cross-s'ection through earth formations and a well bore, and-illustrative of wellcompletion systems according to the present invention; and v 1 FIG. 2 is a diagrammatical view illustrating acentral concept of the present invention.

DESCRIPTION OF THE INVENTION 7 Referring now to FIG. 1, a wellcompletion system is illustrated in vertical cross-section through a producing well which traverses earth formations. The borehole 10, which is drilled through the earth formations, typically has sections ll, 12, and 13 of different diameter where the bore size decreases as the depth of the well increases. In the particular illustration of FIG. 1, two horizontal zones A and B of earth formations are illustrated from which it is desired and-intended to separately and independently produce hydrocarbons or 'gas. In the completing of this-well, a first tubular assembly which is called casing is disposed between. the earths surface and to a selected strata depth, and the annulus .15 between the casing and the borehole section 10 is cemented in a well-known manner. Dependent from thecasing 14 is a liner 16, which is simply a tubular assembly telescopically received by the casing 14 and which extends below thecasing to a lower or deeper strata depth. The liner 16 is attached to the lower end of the casing by a suitable, well-known cone and slip locking arrangement 17. The cone and slip arrangement typically permits insertion of the liner through the casing to the desired location. Actuation of the slip and cone arrangement anchors the linerto the casing. The annulus 18 between the liner l6 and the borehole section 12 is also suitably cemented. Finally, depending from the liner l6 is a packer bore receptacle assembly 19 (sometimes called PBR assembly) which is a tubular assembly telescopically received by the liner l6 and which extends below the liner 16 to the bottom of the borehole section 13. The PBR assembly to the lower end of the liner 16. The hanger arrangement '20 can be hydraulically or mechanically set in any conventional manner. Likewise, the hanger arrangement can be located above or below a bore 22 of the PBR assembly 19 or can be entirely eliminated if the assembly is set on'the bottom of the hole.

Cement is also disposed in the annulus 21 between the borehole section 13 and the packerbore receptacle assembly 19. As illustrated, when the casing 14, liner 16, and packer bore receptacle assembly 19 are installed in the borehole, the annulus from the bottom of the hole to the top of the hole is filled with cement which effectively prevents migration of gas and fluids between formations and to the earth s surface. The process and techniques for installing the casing, the liner,

the packer bore receptacle assembly, cementing in place, and cleaning out the cement are well-known in the art.

With the tubular members of the casing 14, liner l6 and PBR assembly 19 disposed in the borehole, a flow conduit for hydrocarbons is provided. To couple the interior of the flow conduit to the producing strata, a perforating device such as a shaped-charged gun (not shown) or the like, is lowered through the conduit and used to perforate the earth strata section A and the earth strata section B, either conjointly or separately so that the earth formations are opened up through perforations to the interior of the conduit. With two producing zones, it is conventional to convey the output from the zones independently to the earths surface by means of separate strings of tubing. in the prior art, this was typicallyaccomplished by use of permanent production packers which were permanently set or anchored in the casing or pipe string. In this type of arrangement, the tubing strings were coupled to the packerdevices. Where remedial or work-over operations were required,-it was necessary to drill out the packers and utilize special equipment for such operations.

Since wells periodically require remedial treatment during their life, the requirement of permanent packers or anchors which dictated drilling operations and use of specialized equipment for treatment is burdensome. In this invention, I have eliminated the need for packers and the need for hold-downs or anchors in connection with a treating operation. Pursuing the method of this invention, a packer bore receptacle assembly 19 has upper and lower packer bore receptacles respectively with bores 22 and 23 which are polished and have a uniform diameter along their lengths. The upper and lower packer bore receptacles are coupled to one another by a tubular casing or pipe 21A and spaced apart so that the bores 22 and 23 are arranged to strad die the earth formation strata B. The bores 22 and 23 may be suitably coated with teflon" or any other suitable preparation to protect the surface of the bores. As discussed heretofore, a perforating means (not shown) places the earth strata B into fluid communication by means of perforations 24 with the bore 41 of the PBR assembly 19 intermediate of the packer bores 22 and 23 of the upper and lower receptacles. Below the lower receptacle is a casing or-pipe 23A which has a bore wall tubing 28. The lower seal assembly 27 includes a series-of annular chevron rings of packing material 29 disposed between upper and lower back-up flanges 30 and 31. The outer diameter of the chevron rings 29 is somewhat greater than the internal diameter of the polished bore 23. The chevron rings 29 are sufficiently resilient to allow their compression when inserted into the bore 23 so that the compression of the chevron rings provides a resilient force and extremely tight fluid seal with respect to the internal diameter of the bore 23. The upper seal assembly 26 similarly includes annular chevron packing rings 32 disposed between upper and lower shoulders 33 and 34, and having an outer diameter somewhat greater than the inner diameter of the polished bore 22. In a similar manner, the rings 32 are sufficiently resilient so that they are compressed when inserted into the bore 22. The upper end of the upper seal assembly is coupled by a short section 35 of a heavy walled tubing string to a production tubing string which extends to the earths surface. With both sealing assemblies in the respective bores, fluids from the lower formation canbe passed to the earths surface via the conduit of the tubing.

The lower packer bore 23 of the PBR assembly 19 includes an upwardly facing flange portion 37. The spacingbetween a downwardly facing bottom shoulder 31 of the lower seal assembly 27 and downwardly facing bottom shoulder 34 of the upper seal assembly 26 is made such that when the bottom shoulder 31 engages the flange 37, the upper shoulder 34 will preferably be spaced slightly above an upwardly facing flange 38 so that downward weight applied to the tubing string 36 is applied to the lower flange 37. The length of the packer bore 22 between its uppermost shoulder and the lower flange 38 can be from 10 to 20 feet with 10 to 12 feet being a popular length. From the description thusfar, it will beseen that the long" string which includes the tubing sections 36, 35 and 28, and the upper and lower seal assemblies 26 and 27 can be inserted through the well casing and lowered until the lower seal assembly 27 lands on the flange 37, at which time the lower shoulder of upper seal assembly 26 is just short of engaging the upper flange shoulder 38. The movement of the tubing string and location of the packer seal assemblies in the packer bores requires only vertical movement. At the same time, the seal assemblies allow the use of maximum size internal diameters within the tubing string sections to handle higher volume fluids for stimulation of the earth formations.

When the sealing assemblies are within the sealing bores 22 and 23, then the packer bores are sealed off by the packing elements 29 and 32 and an enclosed volume 40 is formed between the packer bores 22 and 23 of the upper and lower receptacles. The enclosed volume 40, as shown in FIG. 2, is defined by the bore 41 of the casing intermediate of the upper and lower sealing assemblies 26 and 27. The effective cross-sectional area for the lower seal assembly is designated by the symbol A The effective cross-sectional area across the upper assembly is designated by the symbol A The arrows illustrated on the areas indicate the direction of forces when hydraulic pressure is applied to the areas. The upper packer bore 22 is larger in diameter than the lower bore 23 and would ordinarily contain a larger cross-sectional area. However, the seal assembly 26 has an opening 42 extending longitudinally therethrough and the cross-sectional area of the opening is designated as A The area A is sized so that the effective cross-sectional area across'each of the packer bores is substantially equal. Thus, area A 1 is equal toarea A minus area A When hydraulic pressure is applied to the areas A and A there is no unbalance in.the areas to create forces tending to move the seal assemblies relative to the bores 22 and 23. At the upper end of the opening 42 through the packer seal assembly 26 is an enlarged bore 43 (FIG. 1) which has an upwardly facing shoulder and which received the lower endof a tubular stinger 44. The stinger has a circumferential annular sealing device 46 so that when the stingeris disposed within the bore 43, a sealing relationship is made with respect to the seal assembly. The stinger 44 in turn is coupled to a short string of tubing 45 and can be inserted and removed by straight up and down motion.

' held in place by the weight on the upper seal assembly and to accommodate changes in tubing length due to temperatureplnhibiting fluid is introduced into the upper. zone before connecting the short string to the While there have been described what are at present fications as fall within the true spirit and scope of the upper seal assembly. The lower zone can be acidized for example with hydrochloric acid, and flushed in a well-known manner. The upper zone, that is, the zone between the upper and lower receptacles then can be treated with hydrochloric acid by pumping such acid down the short string and flushed in a well-known manner. Because the effective areasacross the packer seals are substantially equal, there is no net effect upon the seal assemblies tending to move them because the upwardly directed force resulting from the piston action on the upper seal assembly is counteracted by the downwardly directed force on the lower seal assembly.

During an acidizing treatment, occasionally the'tubing string will alter its length because of temperature changes and thus the tubing can shorten. The length of the upper packer bore receptacle is long enough to permit the movement of the seals during the treatment.

However, during production of the well, the seals are retained in position so they do not incur wear during operation and consequently the seals last longer.

Summing up the present system, the long string perferably includes a section 28 of heavy 2 /8 in., 8.70 lbs. tubing between the seal assemblies, a section 34 of 2% in., 6.50 lbs. tubing to a location above the end of the casing 14, and then a string of tubing 36 of 3% in., 10.30 lbs. tubing to the surface. When the sealing assembly 27 is landed on flange 37, additional weight should be applied to provide compression to the'tubing. The short string can include 3% in. and 2% in. tubing with a stinger to seal in the bore 43. Both Zones A and B can then be independently and sequentially treated with acid without requiring any further equipment such as hold-downs or removal of the strings from the well bore.

invention.

What is claimed is:

'1. A method for treating at least two spaced-apart strata in a well bore traversing earth formations where said strata ai e opened to the interior of a tubular assembly and the assembly has upper and lower packer bores disposed to straddle the upper strata,

closing off said upper and lower packer bores with substantially equal, effective cross-sectional upper and lower areas while providing with a first string of tubing a flow conduit through said packer bores where the flow conduit extends from the earths surface to the lower strata,

connecting a second tubing string through the closed upper packer bore to the volume defined between the upper and lower areas, and

applying weight on the first string of tubing while introducing a fluid to the upper strata through the second string of tubing.

2. A method for treating at least two spacedapart strata in a well bore traversing earth formations where said strata are opened to the interior of a tubular assembly and the assembly has upper and lower packer bores-disposed to straddle the upper strata,

closing off said upper and lower packer bores with substantially equal, effective cross-sectional upper and lower areas while providing with a first'string of tubing, a flow conduit through said packer bores where the flow conduit extends from the earths surface to the lower strata,

applying weight on the first string of tubing to accommodate changes in tubing length due to temperature,

lowering a second tubing string to the upper packer bore and introducing an inhibiting fluid to volume defined between the upper and lower areas,

connecting said second tubing string through the closed upper packer bore to the volume defined between the upper and lower areas,

introducing acid through said first string of tubing to said lower strata,

flushing said acid from said lower strata,

introducing acid through said second string of tubing to said upper strata, and

flushing said acid from said upper strata.

3. A method for completing a well traversing earth formations comprising the steps of:

locating a tubular packer bore receptacle assembly having upper and lower packer bores in a borehole so that such packer bores straddle an earth strata for production of hydrocarbons, cementing said receptacle assembly in such a location and placing said earth strata into fluid communication with the bore of such packer bore receptacle assembly intermediate of such upper and lower packer bores closing off the lower and upper packer bores with packingmeans associated with a string of tubing to form an enclosed volume between said lower and upper packer bores where said enclosed volume is defined by the bore of packer bore receptacle assembly and the upper and lower cross-sectional areas exclusive of the crosssectional area of such string of tubing,

introducing a well treating fluid under pressure through said upper packing means to said enclosed volume where said upper and lower cross-sectional areas are adjusted to substantially balance the said upper and lower cross-sectional areas to effectively equal amounts thereby to equalize the upward and downward forces on the string of tubing within said enclosed volume and treating the earth strata intermediate of said upper and lower packer bores,

4. Apparatus for use in oil and gas wells which traverse earth formations comprising:

a packer bore receptacle assembly adapted for cementing in place in a borehole, said receptacle assembly having upper and lower packer bores,

packer sealing means including an upper packer sealing assembly and a lower packer sealing assembly, said sealing assemblies being constructed and arranged for a sliding and sealing reception respectively in said upper and lower packer bores, said sealing assemblies being coupled to one another and spaced-apart by a section of tubing so that when said upper packer sealing assembly and said lower packer sealing assembly are slidingly and sealingly received in said upper and lower packer bores that upper and lower cross-sectional areas are defined,

means defining a flow conduit through said upper cross-sectional area, said flow conduit means being sized in cross-sectional area relative to said upper cross-sectional area whereby the effective areas of said upper and lower cross-sectional areas are substantially equal.

5. The apparatus of claim 4 wherein .said upper packer bore has a first polished uniform diameter extending between a first, inwardly extending shoulder and a second, outwardly extendl g ing shoulder, where said second shoulder is disposed above said first shoulder,

said lower packer bore has a second polished uniform diameter extending between a third, inwardly extending shoulder and a fourth, outwardly extending shoulder, where said fourth shoulder is disposed above said third shoulder,

said upper and lower packer sealing assemblies respectively having first and second sealing elements thereon, fifth and sixth downwardly facing shoulders, respectively located below each of said sealing elements, said sectionof tubing spacing, said fifth and sixth shoulders from one another so that upon engagement of the fifth shoulder with the third, inwardly extending shoulder, that the sixth shoulder is located above the first, inwardly extending shoulder.

6. The apparatus of claim 5 wherein said first and second sealing elements are slightly compressible and slightly greater .in diameter than the diameters of the respective packer bores.

7. The apparatus of claim 4 wherein said flow conduit means includes an upper polished bore with an inwardly extending shoulder and a tubular member constructed and arranged for sliding and sealing reception into said upper polished bore and engagement with said inwardly extending shoulder.

8. The apparatus of claim 4 wherein said packer bore receptacle assembly includes means for anchoring said assembly within another tubular well member.

9. The apparatus of claim 4 wherein the effective area of said upper cross-sectional area is defined by the diameter of said upper packer bore less the crosssectional area for said flow conduit and the crosssectional area for said section of tubing and the effective area of said lower cross-sectional area is defined by the diameter of said lower packer bore less the crosssectional area for said section of tubing. 

1. A method for treating at least two spaced-apart strata in a well bore traversing earth formations where said strata are opened to the interior of a tubular assembly and the assembly has upper and lower packer bores disposed to straddle the upper strata, closing off said upper and lower packer bores with substantially equal, effective cross-sectional upper and lower areas while providing with a first string of tubing a flow conduit through said packer bores where the flow conduit extends from the earth''s surface to the lower strata, connecting a second tubing string through the closed upper packer bore to the volume defined between the upper and lower areas, and applying weight on the first string of tubing while introducing a fluid to the upper strata through the second string of tubing.
 2. A method for treating at least two spaced-apart strata in a well bore traversing earth formations where said strata are opened to the interior of a tubular assembly and the assembly has upper and lower packer bores disposed to straddle the upper strata, closing off said upper and lower packer bores with substantially equal, effective cross-sectional upper and lower areas while providing with a first string of tubing, a flow conduit through said packer bores where the flow conduit extends from the earth''s surface to the lower strata, applying weight on the first string of tubing to accommodate changes in tubing length due to temperature, lowering a second tubing string to the upper packer bore and introducing an inhibiting fluid to volume defined between the upper and lower areas, connecting said second tubing string through the closed upper packer bore to the volume defined between the upper and lower areas, introducing acid through said first string of tubing to said lower strata, flushing said acid from said lower strata, introducing acid through said second string of tubing to said upper strata, and flushing said acid from said upper strata.
 3. A method for completing a well traversing earth formations comprising the steps of: locating a tubular packer bore receptacle assembly having upper and lower packer bores in a borehole so that such packer bores straddle an earth strata for production of hydrocarbons, cementing said receptacle assembly in such a location and placing said earth strata into fluid communication with the bore of such packer bore receptacle assembly intermediate of such upper and lower packer bores, closing off the lower and upper packer bores with packing means associated with a string of tubing to form an enclosed volume between said lower and upper packer bores where said enclosed volume is defined by the bore of packer bore receptacle assembly and the upper and lower cross-sectional areas exclusive of the cross-sectional area of such string of tubing, introducing a well treating fluid under pressure through said upper packing means to said enclosed volume where said upper and lower cross-sectional areas are adjusted to substantially balance the said upper and lower cross-sectional areas to effectively equal amounts thereby to equalize the upward and downward forces on the string of tubing within said enclosed volume and treating the earth strata intermediate of said upper and lower packer bores.
 4. Apparatus for use in oil and gas wells which traverse earth formations comprising: a packer bore receptacle assembly adapted for cementing in place in a borehole, said receptacle assembly having upper and lower packer bores, packer sealing means including an upper packer sealing assembly and a lower packer sealing assembly, said sealing assemblies being constructed and arranged for a sliding and sealing reception respectively in said upper and lower packer bores, said sealing assemblies being coupled to one another and spaced-apart by a section of tubing so that when said upper packer sealing assembly and said lower packer sealing assembly are slidingly and sealingly received in said upper and lower packer bores that upper and lower cross-sectional areas are defined, means defining a flow conduit through said upper cross-sectional area, said flow conduit means being sized in cross-sectional area relative to said upper cross-sectional area whereby the effective areas of said upper and lower cross-sectional areas are substantially equal.
 5. The apparatus of claim 4 wherein said upper packer bore has a first polished uniform diameter extending between a first, inwardly extending shoulder and a second, outwardly extending shoulder, where said second shoulder is disposed abOve said first shoulder, said lower packer bore has a second polished uniform diameter extending between a third, inwardly extending shoulder and a fourth, outwardly extending shoulder, where said fourth shoulder is disposed above said third shoulder, said upper and lower packer sealing assemblies respectively having first and second sealing elements thereon, fifth and sixth downwardly facing shoulders, respectively located below each of said sealing elements, said section of tubing spacing, said fifth and sixth shoulders from one another so that upon engagement of the fifth shoulder with the third, inwardly extending shoulder, that the sixth shoulder is located above the first, inwardly extending shoulder.
 6. The apparatus of claim 5 wherein said first and second sealing elements are slightly compressible and slightly greater in diameter than the diameters of the respective packer bores.
 7. The apparatus of claim 4 wherein said flow conduit means includes an upper polished bore with an inwardly extending shoulder and a tubular member constructed and arranged for sliding and sealing reception into said upper polished bore and engagement with said inwardly extending shoulder.
 8. The apparatus of claim 4 wherein said packer bore receptacle assembly includes means for anchoring said assembly within another tubular well member.
 9. The apparatus of claim 4 wherein the effective area of said upper cross-sectional area is defined by the diameter of said upper packer bore less the cross-sectional area for said flow conduit and the cross-sectional area for said section of tubing and the effective area of said lower cross-sectional area is defined by the diameter of said lower packer bore less the cross-sectional area for said section of tubing. 